title: Viability and proliferation potential of adipose-derived stem cells following labeling with a positron-emitting radiotracer.
abstract: OBJECTIVE
  Adipose-derived stem cells (ASCs) have promising potential in regenerative medicine and cell therapy. Our objective is to examine the biological function of the labeled stem cells following labeling with a readily available positron emission tomography (PET) tracer, (18)F-fluoro-2-deoxy-D: -glucose (FDG). In this work we characterize labeling efficiency through assessment of FDG uptake and retention by the ASCs and the effect of FDG on cell viability, proliferation, transdifferentiation, and cell function in vitro using rat ASCs.
  
  
  METHODS
  Samples of 10(5) ASCs (from visceral fat tissue) were labeled with concentrations of FDG (1-55 Bq/cell) in 0.75 ml culture medium. Label uptake and retention, as a function of labeling time, FDG concentration, and efflux period were measured to determine optimum cell labeling conditions. Cell viability, proliferation, DNA structure damage, cell differentiation, and other cell functions were examined. Non-labeled ASC samples were used as a control for all experimental groups. Labeled ASCs were injected via tail vein in several healthy rats and initial cell biodistribution was assessed.
  
  
  RESULTS
  Our results showed that FDG uptake and retention by the stem cells did not depend on FDG concentration but on labeling and efflux periods and glucose content of the labeling and efflux media. Cell viability, transdifferentiation, and cell function were not greatly affected. DNA damage due to FDG radioactivity was acute, but reversible; cells managed to repair the damage and continue with cell cycles. Over all, FDG (up to 25 Bq/cell) did not impose severe cytotoxicity in rat ASCs. Initial biodistribution of the FDG-labeled ASCs was 80% + retention in the lungs. In the delayed whole-body images (2-3 h postinjection) there was some activity distribution resembling typical FDG uptake patterns.
  
  
  CONCLUSIONS
  For in vivo cell tracking studies with PET tracers, the parameter of interest is the amount of radiotracer that is present in the cells being labeled and consequent biological effects. From our study we developed a labeling protocol for labeling ASCs with a readily available PET tracer, FDG. Our results indicate that ASCs can be safely labeled with FDG concentration up to 25 Bq/cell, without compromising their biological function. A labeling period of 90 min in glucose-free medium and efflux of 60 min in complete media resulted in optimum label retention, i.e., 60% + by the stem cells. The initial biodistribution of the implanted FDG-labeled stem cells can be monitored using microPET imaging.
authors.affiliation: Department of Radiology, University of Manitoba, Winnipeg, Canada. e.elhami@uwinnipeg.ca
authors.forename: Esmat
authors.initials: E
authors.lastname: Elhami
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Goertzen
authors.forename: Bo
authors.initials: B
authors.lastname: Xiang
authors.forename: Jixian
authors.initials: J
authors.lastname: Deng
authors.forename: Chris
authors.initials: C
authors.lastname: Stillwell
authors.forename: Shadreck
authors.initials: S
authors.lastname: Mzengeza
authors.forename: Rakesh C
authors.initials: RC
authors.lastname: Arora
authors.forename: Darren
authors.initials: D
authors.lastname: Freed
authors.forename: Ganghong
authors.initials: G
authors.lastname: Tian
mesh_terms: D000273:Adipose Tissue / Q000166:cytology*; D053687:Adult Stem Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D054338:Cell Transdifferentiation / Q000187:drug effects; D005240:Feasibility Studies; D019788:Fluorodeoxyglucose F18 / Q000009:adverse effects* / Q000378:metabolism; D007553:Isotope Labeling / Q000009:adverse effects*; D008297:Male; D049268:Positron-Emission Tomography; D051381:Rats; D011917:Rats, Inbred Lew
chemical_list: D019788:Fluorodeoxyglucose F18